Three-dimensional horn antennas are commonly used in various applications such as communication systems, radar, imaging, and radio astronomy. In these applications, the horn antenna is used either as an independent antenna or as a feeder for its related reflector antenna. Three-dimensional horn antennas are usually bulky, expensive, and difficult to integrate with other components of a system or device.
Circularly polarized (CP) antennas are typically used in satellite and mobile communication systems. CP antennas have certain advantages over linearly polarized antennas. For example, CP antennas are less sensitive to antenna axial rotation and have less delay spread. Planar CP antennas are typically broadside structures. As well, most CP antennas have a complex feed network and a multi-layer substrates topology, which increases the overall cost and dimensions of the antennas.